High frequency coil transformer switch



April 19, 1960 E. s. GOODRIDGE 2,933,583

HIGH FREQUENCY con. TRANSFORMER swI'rcH Filed June 6, 1958 2 Sheets-Sheet 1 T INVENTOR. sow/mo s. 0000mm ATTORNEY P 1960 E. s. sooomoss 2,933,583

HIGH FREQUENCY COIL TRANSFORMER SWITCH Filed June 6. 1958 2 Sheets-Sheet 2 EDWARD GDOPRIDGE ATTORNE Y United States Patent HIGH FREQUENCY COIL TRANSFORMER SWITCH Edward S. Goodridge, Scarsdale, N.Y., assignor to Induction Heating Corporation, Brooklyn, N.Y., a corporation of New York Application June 6, 1958, Serial No. 740,405 4 Claims. (Cl. 219-10.75)

This invention relates to a switch for high frequency high current applications, and more particularly is conthe usual power source used with induction heating In general, the equipment consists of'the' equipment. tank circuit for generating the power, terminals for the connection of load coils to an output transformer, and

a switch for cutting off the tank circuit where the high frequency current is generated. The disadvantage of apparatus of this kind in a production operation where the high frequency circuit is incidental to the manufacture of some product and a single load coil is being driven is rather obvious, because it calls for substantial periods of shutdown. Also, it means that in the induction heating equipment there is a transformer or tank circuit for each load coil and there is, accordingly, a serious limitation of the capacity of a given installation.

It is, therefore, a fundamental object of this invention to provide a switch assembly for use in connecting load coils to a single transformer to practically double the capacity of the equipment.

, Other objects and advantages of the invention will in part be obvious and in part appear hereinafter.

The invention, accordingly, is embodied in a switching apparatus suitable for connection to a high frequency output transformer to bring terminals of the circuit into a single plane and there forming a branch such that two load coils may be connected to the said terminals through the intermediary of a switch mechanism having its contact points in a plane, such that one of the said coils may be applied to the load while the other is simultaneously disconnected.

Reference to the drawings will illustrate the invention in greater detail.

Figure 1 is an isometric view of the complete assembly showing the switch mechanism itself;

Figure 2 is an exploded view of the device, correspondingto Figure 1, showing the form of the several parts and details of their construction;

normally only a" I Patented Apr. 19, 1960 single load coil consisting of l, 3, 5, 7, or as many turns as the particular production application calls for, is constructed of copper tubing, as a typical material, and mounted on blocks matching 12 and 13 so that, when it is put in place, it is fitted over bolts 15, 16, etc., and fastened in place.

The switch mechanism of my invention employs a basic mounting structure matching that of the conventional power connection to an output transformer and as shown in Figure 1, the switch mechanism consists of a pair of conduits adapted for connection to the tank circuit, which pair of conduits is brought forward a distance sufficiently large to permit mounting a pair of load coils and, at that distance, electrical termini are brought to a single plane and the switch mechanism provided for applying the electrical power to one or the other of the coils.

Specifically mounting blocks 21 and 22 form the base of the switch mechanism, which blocks are provided with the central connection for the cooling water con duits 23.and 24 and also are provided with holes 25, 26,

j etc., suitable for matching the bolts 16 and 15 on the transformer to permit mounting the block and bolting it in place. Conduits 30 and 31 are connected to the blocks 21 and 22, for example by integral joining, and it is to be noted that in keeping with good practice in high frequency current applications, conduits 30 and 31 are made of thin cross section but wide area so that they may be brought into very close proximity to each other while separated by the insulating wafer 32. Conduits 30 and 31 are held in fixed relationship to each other by means of bolts like 33 mounted in conventional insulating style by means of insulators 35 with washers and nuts 37 fastening them in place.

Conduits 30 and 31 are extended in length a minimum desired distance from the tank for the production operation contemplated and are then turned at right angles to their direction as shown, each of the conduits then terminating in a connection block 42 and 43 corresponding in physical form to blocks 13 and 12. Insulating wafer 44 is placed against the forward face of the conduits 30 and 31, the wafer having a central sym- Figure 3 is a plan view of the contact surface of the switch handle showing the structure and the means for making the desired contacts in an installation; and

Figure 4 is a section through the contact element along the line 4-4 of Figure 3.

Referring now to Figure 1, 10 represents in general form a tank housing for the transformer and power circuit suitable for generating the high frequency currents useful in induction heating applications, and 11 i1,- lustrates the typical mechanism by which the leads are brought out for application to a load. In general, the leads consist of a pair of conductive blocks 12 and 13 separated by an insulating means 14.

It is to be understood that this. much of the mechanism as shown is virtually a conventional physical setup and that in general, the apparatus is such that a conventional metrically placed section removed therefrom. Mounted against the wafer 44 to form a sandwich with the conduits is the switch block 50, which is cut to the configuration of the insulating wafer 44 and is formed with terminal blocks 51 and 52 at its respective ends, matching the terminal blocks of the conduits which, as noted, match blocks 13 and 12 on the tank circuit. The physical means by which the connection is made consists of a plurality of bolts 53, 54, 5S and 56 which pass through the switch block and are fastened in place insulated from one of the conduits. Copper tube conduits 23 and 24 are matched by conduit 57 which is formed in switch block 50. The cooling water circuit is through conduit 23 to the orifice 23' in block 42, thence through such load coil as is connected to the block, returned to the terminal block 51 from which it passes into orifice 57' and conduit 57, through such load coil as is connected to terminal block 52, and returned to conduit 24, which has its orifice in block 43, and thence to the block 22. Cooling of high frequency induction heating coils. is a conventional operation and the mechanical arrangement by means of which cooling water is circulated through the coils involves the provision of a complete water circiiit such as that outlined.

To complete the electrical circuit, contact block 60 is integrally joined to conduit 30 while being separated from contact block 61, which, in turn, is integrally joined to conduit 31. These blocks are separated by the insulating wafer 32 and have their frontal contact surfaces 60' and 61 brought forward to a plane such that they are flush with the face of switch block 50. For completing the electrical circuit to the load coils, bolt 70 serves as a pivotal support on the switch block 59. Centered on the bolt 71') is the switch contact block 71 which consists simply of a polygonal block which serves as a conductive bridge. In contact with the switch block 50, contact block 71 has trapezoidal undercut areas 72 and 73 undercut to define raised areas 74 and '75 to form a bridge for electrical contact with either one or the other of the switch blocks as and 61. Areas 74 and 75 can be completely rectangular to match 66 and 61, the true consideration being to provide a large enough area of contact to conduct the current. The switch contact block 71 is pivoted on the bolt 79 and held in place by means of spring washer 76 and nut 77. For convenience in manipulating the switch fromone position to another and thus changing load coils. applied to the tank circuit, the contact block 71 is provided with an extended handle 73, which, of course, is insulated with cover 79 so that it can be manually manipulated. Further, for providing the proper degree of maneuverability in the handle and switch contact block, pin 30 is placed on the block 50 and the'lower edges of the switch block 71 are formed so that the pin serves as a detent which prevents movement of the switch handle beyond the designated contact position.

In operation, it will be seen that when the switch handle is turned to the position shown in Figure 1, the electrical path is through the load coil on the side to which the switch handle is turned. The circuit is through conduit 319, block 6%, switch contact block 71 (face 75, body 71, face 74) to block 50, through the load coil attached to block 52 and returned to block 43 and conduit 31. Thus, contact block '71 bridges the gap from block 60 (contact face no) to block 50, thereby short circuiting blocks 42 and 51 and the load coil connected thereto.

To reverse positions, the switch handle 79 is pivoted over to its opposite position, whereupon blocks 43 and 52 and the coil connected thereto are short circuited. In this position, current flow is from block 21, to conduit 30, to block 42, through the load coil attached thereto, to block 51, block h, contact block 71 (face 75, body 71, face 74), to block 61, to conduit 31, and to block 22.

"With this arrangement it is possible to power a pair of load coils from a single transformer without cutting off current from the tank circuit when the work piece in the load coil is being changed. In switching from one coil to the other using the mechanism in accordance with this invention a momentary partial short circuit of both coils occurs when the handle is vertical, but this is or" no practical concern in operation.

Materials of construction are conventional. That is, copper for conductivity and price is virtually essential for all parts which serve as conductors. Insulating wafer 32 is preferably of polyethylene or any equivalent insulator; plastics are preferred in that they permit some compression, because of their flexibility. Insulators used with the bolts are preferably polyethylene, but also may be equivalent plastic or other ceramic.

Though in general the use of an insulating wafer to separate the conductors 30-31 and 30, 31-50 is con,- venient, it is not always necessary. In some installations where the processing is clean and no smoke, particles of solder or brazing metal are spattered into the atmosphere,

an air gap corresponding to that which has herein been.

called an insulating wafer will serve as a good insulator. Also, terminal blocks 42, 51 and 43, 52 represent one preferred form of mechanical connection for the load coil. It is feasible in many instances to utilize a load coil having no corresponding blocks, but merely consisting of conduit equipped with nipples to connect with orifices 23, 57'. In such instances, the switch may be formed without terminal blocks 42, 51 and conduits 30, 31 and 50 merely terminate in the orifice to which the load coil is connected.

Though the invention has been described with reference to only a single example, it is to be understood that variations thereof may be adopted without departing from its spirit or scope.

What is claimed is:

1. A switch assembly for high frequency applications, comprising a pair of conduits, means at one end of said conduits for connection to a source of high frequency current, said conduits being of a broad width and small thickness and separated from each other by an insulating medium and being in close proximity to each other along their broader dimensions to form a sandwitch, a switch.

block at right angles thereto at the other end of said conduits and being separated from said. conduits by means of an insulating medium, thereby forming a double circuit, terminal means on each end of said switch block for connecting a load coil thereto, and means for conducting the high frequency current to a selected one of said terminal means, consisting of a contact block in electrical contact with each of said conduits, one face of each said contact block being in the plane of said switch block, and means on said switch block carrying a pivoted bridging means for making electrical contact from a selected one of said contact blocks to said switch block.

2. In an apparatus for switching high frequency electric currents, the improvement which comprises bringing planar electrical conduits to load coils arranged in parallel and providing switch means so that only one of said coils. is connected to the power gmrce at a given time, said improvement comprising, at a plant intermediate said load coils, providing points for electric contact with each of said planar conduits in said plane, establishing one point in common for said coils electrically, and providing means for bridging from said common point to said other points one at a time.

3. In an apparatus for switching high frequency electric currents, wherein electric conduits are brought to load coils, switch means for connecting one coil at a time to a power source, said switch providing means for electric, contact with said conduits consisting of a first conductive block, having a planar face, insulating means separating said block from said conduits, second and third contact blocks separately electrically connected one to each of said conduits and having contact faces coplanar with the planar face of said first block, a conducting bridging contact pivotally mounted on said first block and pivotable to bridge from said first block to one of said second and third blocks.

4. Apparatus in accordance with claim 3 in which said conduits are wide in relation to their thickness and extend at right angles to each other to define said intermediate point for switching.

References Cited in the file of this patent UNITED STATES PATENTS 

